Add bin/notebook script to start Phoenix + Livebook together

Starts Phoenix with a named node and Livebook attached to it on
port 8081. Single command, Ctrl-C stops both.

bin/notebook

@@ -0,0 +1,40 @@
+#!/bin/bash
+# Start Phoenix + Livebook together. Livebook attaches to the Phoenix node
+# and gets full access to Repo, Scorer, Weather, etc.
+#
+# Usage: bin/notebook
+# Then open http://localhost:8081
+
+set -e
+
+COOKIE="microwaveprop_nb"
+NODE="prop@$(hostname -s)"
+PORT="${LIVEBOOK_PORT:-8081}"
+NOTEBOOK="notebooks/algorithm_analysis.livemd"
+
+echo "Starting Phoenix on :4000 and Livebook on :${PORT}..."
+echo "Livebook will be at http://localhost:${PORT}"
+echo ""
+
+# Start Phoenix in background with a node name
+elixir --sname prop --cookie "$COOKIE" -S mix phx.server &
+PHOENIX_PID=$!
+
+# Wait for the node to come up
+sleep 3
+
+# Start Livebook attached to the Phoenix node
+LIVEBOOK_HOME="$(pwd)/notebooks" \
+  livebook server \
+  --port "$PORT" \
+  --default-runtime "attached:${NODE}:${COOKIE}" \
+  --open "$NOTEBOOK" &
+LIVEBOOK_PID=$!
+
+# Trap ctrl-c to kill both
+trap "kill $PHOENIX_PID $LIVEBOOK_PID 2>/dev/null; exit" INT TERM
+
+echo "Phoenix PID: $PHOENIX_PID, Livebook PID: $LIVEBOOK_PID"
+echo "Press Ctrl-C to stop both."
+
+wait

lib/mix/tasks/notebook.ex

@@ -1,27 +1,15 @@
 defmodule Mix.Tasks.Notebook do
-  @shortdoc "Start Phoenix + Livebook at localhost:8081/notebooks/algorithm_analysis.livemd"
+  @shortdoc "Print instructions for starting the analysis notebook"
   @moduledoc false
   use Mix.Task
 
   @impl Mix.Task
   def run(_args) do
-    hostname = :inet.gethostname() |> elem(1) |> List.to_string()
-    cookie = "microwaveprop_notebook"
-    node = "prop@#{hostname}"
-
     IO.puts("""
-    Start Phoenix with a node name first:
+    Run bin/notebook to start Phoenix + Livebook together.
 
-        iex --sname prop --cookie #{cookie} -S mix phx.server
-
-    Then in another terminal:
-
-        LIVEBOOK_NODE=#{node} LIVEBOOK_COOKIE=#{cookie} livebook server \\
-          --port 8081 \\
-          --default-runtime attached:#{node}:#{cookie} \\
-          --open notebooks/algorithm_analysis.livemd
-
-    Livebook will be at http://localhost:8081
+    Livebook will be at http://localhost:8081 with full access to
+    Repo, Scorer, BandConfig, Weather, and all app modules.
     """)
   end
 end